1. Field of the Invention
The present invention relates to an apparatus for work on electric power distribution equipment. More particularly, it relates to an apparatus for removing a preform or tie wire wrapped about a live power transmission line typically at or near an insulator, but not only in these locations.
2. Description of the Prior Art
At times it has been necessary to service various parts of an electrical power transmission system, such as by replacing a transformer, without interrupting service. In doing so, the crew members had to work on the equipment in the presence of live transmission lines or conductors.
It was common practice for the electrical wire to have a preformed armor wire, or preform, coiled about it for strength against tension and bending. The preform usually had to be removed from the live electrical line to work on the electrical equipment.
In order to avoid electrical shock, the prior art offered several types of elongate insulative poles, called hot sticks, to which various kinds of preform removal tools could be attached. With the preform remover at a far or distal end from the crew member, power line work was relatively safe, albeit cumbersome. It was difficult to make connection with an end of the preform while manipulating an elongate hot stick.
Example preform removal tools included U.S. Pat. No. 1,045,679 and U.S. Pat. No. 2,096,244 which had removal tools with small engaging hooks or flanges on their far ends. These tools were undesirable, as disclosed above, because removal of preforms first required connection of the engaging portion of the tool to the preform. This often required several attempts to successfully hook the ends of the preform.
Additional examples included U.S. Pat. No. 1,819,170; U.S. Pat. No. 2,633,160 and U.S. Pat. No. 2,556,663 which had rotary unwrapping or wrapping tools on their far ends. These tools were undesirable because they had to be maintained substantially perpendicular to the conductor while the tool was manipulated during preform removal. This frequently rendered the tools incapable of removing a relatively inaccessible preform. Examples of inaccessible preforms were where the preform was recessed in an enclosure, was obstructed or where the crew member could not otherwise position the tool substantially perpendicular to the power line.
Additionally, the tools of the previously mentioned U.S. Pat. Nos. 1,819,170 and 2,633,160 were further undesirable because they could only engage the preform through a narrow slot. The tool of U.S. Pat. No. 2,633,160 also required the crew member, after mounting the tool on the power line, to connect with a loop or eyelet at the preform end with one of a pair of horns of a T-shaped hook. Finally, the tool of U.S. Pat. No. 2,566,663 did not provide any specific provision for preform unwrapping.
Other apparatus in the transmission line servicing field, but generally unrelated to preform removal, included U.S. Pat. No. 3,021,875; U.S. Pat. No. 3,959,869 and U.S. Pat. No. 4,132,441.